1. Field of Invention
The present invention relates to a manufacturing method of an optical information record carrier and, more particularly, to a manufacturing method of an optical information record carrier that has a plurality of layers of reflective layers recorded with information, such as a dual-layer dual-side optical disk.
2. Related Art
An optical disk is a storage medium that records data signals in the form or recess and protrusion portions/pits. Since the optical disk has a high data storage density, the data access is in a non-contact way and the stored data can last for a longer time, thus it is widely used in storing voice, video images and large-size software. The conventional optical disk (e.g. CD) has only a one side and one layer. A CD with a diameter of 12 centimeters has a capacity of about 650MB. The read-only memory type digital versatile disks (DVD-ROM) introduced in recent years have the following four specifications: one side and dual layers, one side and one layer, dual surfaces and one layer, and dual surfaces and dual layers. For a DVD-ROM with a diameter of 12 centimeters, the dual-layer dual-side disk has a capacity of 4.7GB (DVD-5), and the dual-layer dual-side one has a capacity of 17GB (DVD-18). Currently, DVD-5 (4.7GB), DVD-9 (8.5GB) and DVD-10 (9.4GB) are available on the market, yet there is no commercialized DVD-18 (17GB) available mainly because of the bottleneck difficulty in the manufacturing process.
The usual manufacturing process of the dual-layer dual-side DVD-ROM is to adhere two dual-layer one-side data recording substrates 10 of 0.6mm thick together, as shown in FIGS. 4a and 4b. One substrate 10 has a first reflective layer 11 and a second reflective layer 12 on one surface with a transparent polymer resin layer 12 in between. The first reflective layer 11 and the second reflective layer 12 are reflecting surfaces that have data pit patterns in recess and protrusion portions. The first reflective layer 11 can be a partial reflective layer made of, for example, Au or Si; the second reflective layer 12 can be a total reflective layer made of Al. Therefore, the data stored on these two layers can be accessed from the other surface of the substrate using an optical read/write device. Adhering the two double-layer data recording substrates 10 by an adherent 14 placed between the second reflective layers 12 of the two substrates 10, one then gets a dual-layer dual-side optical disk.
To make a dual-layer dual-side DVD-ROM, the currently available technologies to form a plurality of data recording layers on a substrate include: the injection molding method, the photo polymer (2P) method and the spin-on and peel (SOAP) method.
Two pieces of stampers etched with signals are disposed at the fixed surface and mobile surface of an injection cavity, respectively. A high temperature and a high pressure are imposed to press a plastic material (e.g. polycarbonate) into the cavity. The male mold (mobile surface) and the female mold (fixed surface) of the cavity are provided with stampers etched with pit patterns, thus forming a thin film with pit patterns on both surfaces. Once a reflective layer is formed on the thin film, it is adhered onto an optical disk substrate. This method requires high temperatures and high pressures and thus has serious erosion on the stampers. Further, the thickness of the thin film made by the injection molding has its lower limit, thus no ultra-thin films can be made. Moreover, thermal stress and inhomogeneous contraction of the plastic often cause distortions of the products so that they do not satisfy the standard and lower the product yield.
The 2P method first coats a layer of highly plastic polymer resin on a stamper. A high pressure is imposed to press the polymer resin against the stamper to copy the pit pattern on the stamper onto the polymer resin. The polymer resin layer is then cured by ultraviolet (UV) light to form a thin film with a pit pattern. This cured thin film is adhered onto another substrate that is etched with a pit pattern and coated with a partial reflective layer, the surface with the pit pattern being facing outward. A total reflective layer is formed on the thin polymer film to form a disc with a dual-layer one-side optical disk. If the total reflective surfaces of two such dual-layer one-side substrates are adhered together face to face, a dual-layer dual-side optical disk can be obtained, such as a DVD-18. The defect of this method is that it needs a high pressure in order to obtain a good pit pattern copy, which will causes serious erosion of the stamper. It is hard to control the yield in the technology of combining the thin film and the substrate due to bubbles and wrinkles.
The SOAP method drops a polymer resin solution onto a spinning stamper so as to spin-coat the polymer resin solution homogeneously over the whole stamper. When the solution vaporizes, a layer of cured thin film with a pit pattern is formed. This thin film is then adhered onto a substrate with a pit pattern surface and a partial reflective layer, the surface with the pit pattern being facing outward. A dual-layer one-side disk is formed by further coating a total reflective layer. A dual-layer dual-side disk is formed by combining two pieces of the dual-layer one-side optical disks with the two total reflective surfaces adhered face to face. This method, however, still needs a process for combining the thin film and the substrate in which bubbles and wrinkles are likely to be produced to lower the yield.
To solve the problems of serious erosion of the stamper and the low yield in the above methods, it is desirable to provide a new manufacturing method.
It is a primary object of the present invention to provide a method for manufacturing an optical information record carrier that can reduce the erosion of the stamper and increase the yield.
Pursuant to the above object, the disclosed method directly forms a reflective layer on a stamper. A radiation setting resin is then employed to adhere a substrate with a pit pattern and a partial reflective layer onto the stamper. This method eliminates the step of making a thin film and adhering the thin film onto the substrate, thus avoiding the problems with bubbles and wrinkles.
The radiation setting resin in the method is applied by spin coating without high temperature and pressure. Therefore, erosion on the stamper is reduced and there is no such problem of distortion due to thermal stress and residual stress.
One disclosed manufacturing method of an optical information record carrier comprises the steps of: forming a first reflective layer on a stamper with a first pit pattern; coating a radiation setting resin layer on the first reflective layer of the stamper; providing a substrate whose one surface is provided with a second pit pattern and coated with a second reflective layer; adhering the surface of the substrate to the stamper with the resin layer being between the substrate and the stamper; radiating and curing the resin layer using a light beam; peeling the stamper off from the first reflective layer; and adhering the surface with the reflective layer of the substrate to that of another substrate.
Another disclosed manufacturing method of an optical information record carrier comprises the steps of forming a first reflective layer on a stamper with a first pit pattern; providing a substrate whose one surface is provided with a second pit pattern and coated with a second reflective layer; coating a radiation setting resin layer on the second reflective layer of the substrate; adhering the surface of the substrate to the first reflective layer of the stamper with the resin layer; radiating and curing the resin layer using a light beam; peeling the stamper off from the first reflective layer; and adhering the surface with the reflective layer of the substrate to that of another substrate.
Other features and advantages of the present invention will be apparent from the following detailed description, which proceeds with reference to the accompanying drawings.